Contacting solids with gaseous fluids



Fe .11,'1941. LE Roi Em 2.415.756

CONTACTING SOLIDS WITH GASEOUS FLUIDS Filed Jan. 23, 1945 Urn/eaters ClbL-or neq Patented Feb. 11, 1947 NITED STATES PATENT OFFHCE Earl J. Le Roi and John H. J ohnsen, Baton Rouge, La., assignors to Standard Oil Development Company, a corporation of Delaware Application January 23, 1945, Serial No. 574,101

This invention relates to apparatus adapted for use in contacting solid particles with gaseous fluids, and more particularly, relates to stripping or purgin entrained volatile material from solid particles.

In certain catalytic operations, such as the catalytic cracking of hydrocarbon oils to produce lower boiling hydrocarbons, hydrocarbon-gases and/or-vapors are entrained with the catalyst or contact particles removed from the contacting or conversion zone and it is preferred practice to remove such vapors and/or gases from the particles before using them in another contacting or conversion step or before regenerating them prior to re-use in another contacting or conversion step.

During catalytic conversion of hydrocarbons as, for example, catalytic cracking, coke or carbonaceous material is deposited on the particles and the spent or contaminated particles withdrawn from a conversion or reaction zone contain entrained hydrocarbon vapors and gases.

Claims. (Cl. 23-288) In the improved design of catalytic cracking units, the catalyst or contact particles are maintained in a dense, dry, fluidized liquid-simulating condition in the reaction zone wherein hydrocarbons in vapor or gas form are contacted with the. solid contact particles. The hydrocarbon vapors or gases pass upwardly through the dense fluidized mixture in the reaction zone and the vaporous reaction products containing only a small amount of entrained solid particles are taken overhead from the reaction zone. The spent or contaminated contact or catalyst particles are withdrawn as a dense fluidized mixture from the bottom of the reaction zone.

The spent or contaminated particles withdrawn from the reaction zone contain entrained hydro-- carbon vapors or gases, and before regenerating the particles it is preferred practice to remove the entrained hydrocarbons in a stripping or purging step to recover the hydrocarbons and to reduce the amount of burning necessary in the regeneration zone.

The present invention relates to an improved design for a stripping or purging section or zone in such a reaction zone. In the preferred form of the reaction vessel the mixture of catalyst or contact particles and hydrocarbon vapors or other reactant is introduced into the bottom portion of a reaction zone through a hollow conical member of chamber provided with a horizontally arranged perforated distribution plate. Surrounding the conical member is' an annular space or chamber formed by a sleeve or skirt depending from the conical member and spaced from the inner wall of the reaction vessel. This skirt extends a distance below the distribution plate and forms with the wall of the vessel an annular stripping section in the lower portion of the reaction vessel.

In the preferred form of our invention the annular stripping section is subdivided into a plurality of stripping sections by a baflie construction. The particular bafile construction disclosed is a disc and doughnut baffle. Steam or other stripping gas is introduced at a plurality of points at the bottom portion of the annular stripping" section and passes upwardly through the stripping section countercurrent to the downfiowing catalyst or contact particles being stripped or purged.

The space below the conical inlet member is reduced in volume by a lower inverted conical memberextending from the skirt and spaced from and substantially parallel to the conical bottom portion of the reaction vessel. In this way the volume below the first mentioned conical inlet member is reduced and this reduces the holding time of the catalyst particles in the stripping section. In the catalytic cracking of hydrocarbons the contaminated catalyst or contact particles are at a high temperature and'prolonged holding of the mixture at this high tern" perature in the presence of steam, which is the preferred stripping and fluidizin'g gas, results in a significant loss of activity.

Provision is also made for maintaining the space between the upper conical inlet member and lower spaced conical member substantially clear of dust particles by extending one or more pipes or tubes into the space and continuously releasing a purging gas into this space.

In the drawing, the figure represents a longitudinal vertical cross-section of a reaction vessel including our improved stripping apparatus.

Referring now to the drawing, the reference character ill designates a reaction vessel provided with an inlet line I2 for introducing a mixture of reactants and the catalyst or contact particles. In the catalyticcrackingof hydrocarbons, the reactant fluid comprises hydrocarbons in liquid or vapor form or partly in liquid and partly in vapor form, such as gas oil, reduced crude oil, whole crude petroleum oil, heavy naphthas, etc.

The catalyst or contact particles in a cracking operation comprise hot regenerated catalyst or contact particles and some of the heat is supplied to the reactants and to the reaction or conversion by the hot regenerated catalyst particles.

tribution plate I6 at its upper end.

In the form of the apparatus shown in the drawing. the reaction vessel i is cylindrical and the perforated distribution plate member or grid is circular and centrally disposed in the lower portion of the reaction vessel It. The diameter of the distribution plate member i6 is less than the internal diameter of the reaction. vesse1 in order to provide an annular space for withdrawing solid particles fromthe bottom portion of the reaction vessel as will be hereinafter described in greater detail.

The velocity of the gaseous reactant fluid passing upwardly in the reaction zone or vessel III is preferably selected to maintain the solid particles in a dense fluidized liquid-simulating dry mixture or bed l8 having a level .indicated at 22 with a dilute phase or dilute suspension thereabove designated at 24. As the vaporous reaction products leave the dense bed or mixture I8, they entrain a small amount of solid particles and this suspension comprises the dilute phase designated at 24. The densefiuidized mixture or bed I 8 is maintained as a mobile and turbulent mass or mixture and in this way insures intimate contact between the gaseous fluid and the contact particles.

In the catalytic cracking of hydrocarbons, the cracking catalyst comprises any suitable cracking catalyst, such as acid-treated bentonite clay, synthetic silica alumina gel, synthetic silica magnesia gel, etc. The catalyst is preferably in powdered or finely divided form in which the particles have a size between about 100 and 400 standard mesh. The preferred catalyst is made up of particles of which about 95% passes through 100 standard mesh and the mixture contains less than 35% of 0 to 20 micron material. With such a catalyst the velocity of the gaseous fluid passing upwardly through the dense bed or mixture I8 is about 0.5 ft./second to 2.0 ftJsecond and under these velocity conditions the density of the mixture forming the dense bed I8 is about lbs./cu. it. to 40 lbs/cu. ft.

The light suspension designated at .24, including the vaporous reaction products, is passed through inlet 25 of separating mean 26 arranged in the upper'portion of the reaction vessel in to separate most of the entrained solid particles from the vaporous reaction products. The separated solid particles are returned to the dense bed or mixture l8 through line or pipe 28 which extends below the level 22 of the-dense bed or mixture l8. The vaporous reaction products leaving the separating means 26 pass overhead through line 32 and may be passed to any suitable equipment to recover desired products.

In the catalytic cracking or conversion of hydrocarbons, the vaporous reaction products are passed to a fractionating system to separat gasoline or motor fuel from gases and higher boiling hydrocarbon constituents. Other forms of separating means may be used or more than one separating means may be used in series for more completely separating the solidparticles from the vaporous reaction products leaving the reaction zone or vessel l0.

Arranged around the periphery of the conical inlet member [4 at the lower portion of the reaction vessel is a stripping zone or section, in-

dicated at 36, which is annular in form and which is formed between the inner wall of the vessel It and a smaller-diameter, concentrically and vertically arranged sleeve or skirt 38 which extends downwardly from the distribution plat member Hi. The upper end or the sleeve or skirt 38 is secured and sealed to the periphery of the conical inlet member I4 to prevent leakage around the edge of the plate member Hi.

The stripping zone or section 36 is provided with a balile construction for effecting intimate contact between thesolid particles and the stripping gas. This baliie construction comprises a disc and doughnut baille construction and is suit- 42 and 44. The annular member 42 is secured to the inner wall of the vessel l0 and projects inwardly and downwardly a short distance. The other annular baiile member 44 is attached to the skirt or sleeve 38 .and projects downwardly and outwardly from said sleeve or skirt and toward the other baflle construction 42. The adjacent lower ends of the annular baffle form a narrowed opening 45 through which the spent or fouled catalyst or contact particles are passed.

The next lower baflle construction comprises a disc 46 which is of inverted V shape in cross section with the apex directly beneath the narrowed opening 45 so that the stream of solid particles is subdivided into two streams as it passes downwardly over the disc. The lower ends of the disc are spaced from the inner wall of the vessel l0 and the skirt 38 to permit downward passage of the solid particles to the next doughnut baille construction.

The next lower doughnut bafile construction comprises inclined annular baiiie members 46 and 52 similar to the annular bailie members 42 and 44 above described. Arranged below the doughnut bafiies 48 and 52 is a, disc baille 54 which is similar to the battle disc 46 above described. Circular pipes 56 and 58 are provided having openings in the upper portions thereof for introducing stripping gas, such as steam, into the lower portion of the annular stripping zone or section 36 below the lowermost disc baiile 54. A feed pipe 62 isprovided which communicates with the annular pipes 56 and 58 for introducing stripping gas thereto. I

While we have shown a certain number of disc and doughnut bailles, it is to be understood that the number may be varied.

Arranged in the lower portion of the stripping section 36 is an inner baiiie ring 66, angular in cross-section and having its upper portion secured to the skirt or sleeve 38 and having its lower portion spaced from the sleeve or skirt 38. An outer ring baille 61, also angular in cross-section, is provided at the lower portion of the stripping section 36 and has its upper portion secured to the inner wall of the reaction vessel It and has its lower portion spaced from the inner wall. The rings 66 and 61 provide a restriction in the cross-section at the base of the stripping ical inlet member I4 and the bottom of the reaction vessel is reduced. The lower conical member I2 is provided with an opening 14 provided with a collar having a serrated lower end at IS. The collar I5 forms an opening into the space I8 between the conical members I and I2 and will be described in greater detail hereinaiter.

Lines or tubes 82 and 84 are provided for introducing gas into the upper portion of the space I8 between the conical members It and I2 to prevent the accumulation of dust or solid particles in this space. As above pointed out, the conical lower baiile member I2 is spaced from the bottom of the reaction vessel ill to provide a space 86 therebetween for conveying stripped or purged catalyst or contact particles from the stripping section 36 to the standpipe 88 leading from the bottom of the reaction vessel I0. Collar I4 is arranged above the standpipe 88 and is co-axial therewith. Some stripping will take place in space 86 which extends the stripping section 36. Because of the smaller passageway the catalyst passes through space 86 at a higher velocity and this gives improved stripping.

The conical baffle member I2 is provided with the opening '85 above described and has the notched or serrated lower end I6. Line or pipe 82 passes through conical bottom I3 and opens into the upper portion of space I8 adjacent and exterior to the upper portion of conical inlet member Id and adiacent the upper part of sleeve or skirt 38. Preferably pipe 82 is positioned below inlet line l2 between conical member I2 and conical bottom I3 to protect it from erosion by the downwardly moving catalyst. Within space T8 line 82 has a branch lineili extending upwardly in space I8 on the opposite side of conical member I8. Pipe 82 has open end.92 and branch pip 88 has open end lit for introducing gas, such as steam or flue gas, into the space I8 between conical members I l and I2 to prevent the accumulation of dust or solid particles in the space I8. The introduced gas vents through the opening It in collar I5 and is evenly distributed to the space 86 by the serrations on collar I5. While we have shown only two lines 82 and 88, it is to be understood that more lines of this character may be used to distribute the introduced gas more evenly into the space 18.

The lower portion of ring 66 attached to the inner wal lot the vessel I 0 below stripping section 38 is preferably serrated or notched to insure even distribution of gas into the stripping section 86. This gas rises from below and some of this gas comes from the bleed gas introduced into space I8 and vented from the space through collar I5. Another portion of this gas comes from the upper portion of standpipe 88 and comprises gas used for fluidizlng the solids in the standpipe.

Gas is preferably introduced into the cone shaped bottom I3 of vessel I 8 through one or more lines 96 to maintain the solid particles in fluidized liquid-simulating condition in the space 86 and some of this gas is released and passes upwardly and into the stripping section 36 by distributing serrations on ring 66. In addition, as the fluidized solids pass through space 86, some additional gas may be liberated by settling of the fluidized mixture of solids to a higher density. Some stripping of the particles may take place in space 85 as the fluidized mixture passes downwardly therethrough.

The conical members I4 and I2 are suitably suppgrted by the conical bottom 18 of the vessel The space 88 between conical member I2 and conical bottom I3 forms a passageway of relatively small volume for conducting the stripped solid particles from the stripping section 38 to the top of standpipe 88. In previous arrangements the space below the conical inlet member I8 was open or unobstructed and a large amount of solid particles accumulated in this space and the catalyst particles were held up in this space in the bottom of the vessel.

The catalyst particles passing from the reaction zone are at a high temperature and the deactivation of the catalyst particles is accelerated-at high temperatures by contact with steam used as a stripping and 'fluidizing gas. In previous arrangements the hold up of the catalyst in the conical bottom of the reaction vessel was about 20% of the total operating time. With the introduction of the lower conical member I2 the total volume in the bottom of the reaction vessel where catalyst Hold up is encountered is reduced by about 37% so that the catalyst is held up for a shorter time in the bottom of the reaction vessel.

The baflle construction 82, 88, etc., in the stripping section 36 increases the efficiency of the stripping step as it results in stripping in a plurality of stages. With the bafile construction, better contact between the catalyst particles and stripping gas is obtained. Other forms of bafiies may be used. With the reduced volume 8-6 the catalyst is held up for a shorter time and deactivation of the catalyst is reduced.

The operation of our apparatus will now ,be described in connection with catalytic cracking of hydrocarbons. Powdered catalyst and hydrocarbon oil vapors, such as gas oil vapors, are passed through line I2 and through distribution plate It to form a dry fluidized liquid-simulating and turbulent mixture I8 in the reaction vessel ID. The temperature during cracking may vary between about 800 F. and l100 F. The catalyst to oil ratio may vary between about 5 to l to 35 to 1 by weight.

During the cracking operation the catalyst particles become fouled or spent by the deposition of coke or carbonaceous material on the particles. The fouled catalyst particles in a fluidized condition and containing entrained hydrocarbon vapors and gases are withdrawn from the dense bed or mixture I8 and passed into the upper part of the strippingv section 86. Stripping gas, such as steam, is introduced into the lower portion of the stripping section 36 through lines 58 and 58. The stripping gas passes upwardly through the stripping section 38 countercurrent to the downward flow of the fluidized catalyst mixture. The baflie construction 62, 88, etc., in the stripping section brings about intimate contact between the catalyst particles and the stripping gas and improved stripping is obtained. The stripping gas and stripped-out vapors and gases pass upwardly into the dense bed or mixture I8 in the reaction vessel I8.

The stripped particles in fluidized condition pass to reduced passageway 88 and then to the standpipe 88 which is used to generate hydrostatic pressure to move the spent and stripped particles to a regeneration zone or vessel (not shown).

The amount of spent catalyst passing through the stripping section 36 in a commercial unit is about 2400 tons per hour and the amount of steam used in stripping is about 9000 lbs. hour. The steam is at a temperature of about 950 F. The velocity of the stripping gas passing upwardly through the stripping section is about 1 ft./second under these conditions.

The catalyst hold up time following the stripping step in our improved design is reduced by about 37%.

While our improved stripping device has been specifically described in connection with catalytic cracking of hydrocarbons to produce gasoline, it is to be understood that our device may be used for removing volatile material from solid or contact particles in other reactions generally and more particularly with other hydrocarbon conversion reactions such as dehydrogenation of butane and butene fractions, aromatization of naphthas, coking of heavy residual oils and the like, and also may be used generally in other catalytic ornon-catalytic reactions involving reactions of organic or inorganic material and not restricted to hydrocarbon material, such as oxidation of alcohols to aldehydes or acids, reduction of oxides or preparation of pure anhydrous hydrogen chloride.

While we have set forth the best form of apparatus known to us, it is to be understood that this is by way of illustration only and various changes and modifications may be made without departing from the spirit of our invention.

What is claimed is:

1'. An apparatus of the character described including a vessel adapted to contain a fluidized bed of solid particles and for contacting gaseous fluid and said solid particles and having a top outlet for gaseous fluid and a bottom outlet for solid particles, an inverted conical inlet member arranged in .the lower part of said vessel provided at its upper end with a horizontally extending perforated plate, said conical member and perforated plate being arranged centrally of said vessel and spaced from the inner wall of said vessel, a vertically arranged baffle member in sealed contact with the upper portion of said conical member extending downwardly therefrom and arranged to provide a space between said inner wall of said vessel and said baiiie member for forming a stripping section for downward flow of said fluidized particles, means for introducing a stripping gas into the lower portion of said space, a second lower inverted conical member having its upper portion sealed to the bottom of said bafile member so arranged as to reduce the volume below said conical inlet member and form a continuation or said space communicating with said outlet for flow of fluidized particles thereto.

2. An apparatus according to claim 1 wherein said vessel has a conical bottom and said second conical member is spaced from said conical bottom and substantially parallel thereto.

3. An apparatus according to claim 1 wherein said second conical member has an opening in its bottom portion and also includes means for introducing a gas into the space between said conical members to prevent accumulation of solid particles therein.

4. An apparatus according to claim 1 wherein said vessel is cylindrical and said bafiie member comprises a sleeve concentrically arranged with respect to said vessel.

5. An apparatus of the character described including a vessel adapted .to contain a fluidized bed of solid particles and for contacting gaseous fluid and said solid particles and having a top outlet for gaseous fluid and a bottom outlet for solid particles, an inverted conical inlet member arranged in the lower part of said vessel provided at its upper end with a horizontally extending perforated plate, said-conical 'member and perforated plate being arranged centrally of said vessel and spaced from the inner wall of said vessel, a vertically arranged baiiie member in sealed contact with the upper portion of said conical member extending downwardly therefrom and below the lower portion of the conical inlet member arranged to provide a space between said inner wall of said vessel and said baifle member for forming a stripping section for downward flow of said fluidized particles, means for introducing a stripping gas into the lower portion of said space, a second inverted conical member below said conical inlet member and having its upper portion sealed to the bottom of said baiile member so arranged as to reduce the volume below said conical inlet member and form a continuation of said space communicating with said outlet for flow of fluidized particles thereto.

EARL J LE ROI. JOHN H. JOHNSEN.

I REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,388,078 Reeves Oct. 30, 1945 

